1. Field of the Invention
This invention relates to a process for the production of hydrocarbons, especially gasoline.
2. Description of the Related Art
In particular, the invention concerns a combination of process steps for the production of gasoline compounds from synthesis gas wherein carbon dioxide being present in the synthesis gas and being formed during the process is separated from the final liquid gasoline compounds.
The synthetic gasoline process is known to take place in two steps: the conversion of synthesis gas to oxygenates and the conversion of oxygenates to gasoline product. These process steps may either be integrated, producing an oxygenate intermediate, e.g., methanol or methanol dimethyl ether mixtures, which along with unconverted synthesis gas is passed in its entirety to the subsequent step for conversion into gasoline or the process may be conducted in two separate steps with intermediate separation of oxygenates, e.g. methanol or raw methanol.
Useful oxygenates include methanol, dimethyl ether and higher alcohols and ethers thereof, but also oxygenates like ketones, aldehydes and other oxygenates may be applied.
In either case conversion of synthesis gas to oxygenates involves heat development in that both the conversion of synthesis gas to oxygenate and the further conversion of oxygenate to gasoline product are exothermic processes.
The production of gasoline by the integrated process scheme is also discussed in U.S. Pat. No. 4,481,305. Hydrocarbons and especially as gasoline are prepared by catalytic conversion in two subsequent reactors of a synthesis gas containing hydrogen and carbon oxides and having a mole ratio CO/H2 above 1 and when the conversion commences a mole ratio CO/CO2 of 5 to 20. Synthesis gas is converted with high efficiency in a first step into an oxygenate intermediate comprising predominantly dimethyl ether (DME) said mixture being converted in a second step into gasoline by the net reaction scheme3H2+3CO−>CH3OCH3+CO2+Heat  (1)CH3OCH3−>1/n(CH2)n+H2O+Heat  (2)(CH2)n represents the wide range of hydrocarbons produced in the gasoline synthesis step. After separation of the hydrocarbon product, unconverted synthesis gas comprising hydrogen and carbon oxides is recycled to the oxygenate synthesis step after CO2 is at least partly removed, e.g. in a CO2 wash.